I read this thread a few weeks ago and thought "I am sooo glad I don't live in humid, damp, funky country anymore." Then...
I get a horse in for legging up with cannon crud. The horse is from So Cal. Where he's from and where he is now has had less than 4" of precip this year. Definitely urine scald.
I called the new owner and reported. New owner happens to be a vet. I knew what I would use. I figured he'd have some magical potion. Not quite.
He told me to make a weak solution of warm water and Dawn dish soap, wash well, remove the crusted area, rinse well. Good grief. That isn't even medicine.
Two applications, four days apart and it is cleared up.